Advanced Queuing - Oracle

Transformation Questions
Messaging Gateway Questions
Why are messages moved to the default AQ exception queue upon
propagation failures for an outbound propagation job?
The MAX_RETRIES parameter of AQ queues controls when AQ moves messages to
an AQ exception queue for a failed dequeue attempt. The default value is NULL,
which resolves to the value 5 in Oracle 9i.
If the parameter value is too small, messages in the queues can be moved into AQ
exception queues if the MGW agent keeps running into failures when processing
MGW subscribers. The AQ messages moved to AQ exception queues cause
unrecoverable failures on the associated MGW subscribers. The MAX_RETRIES
parameter for AQ queues that are used as a propagation source should be set to at
least 16, and preferably a much larger value.
How do I use transformations?
An MGW subscriber can be configured with a transformation to use during an AQ
dequeue for outbound propagation or an AQ enqueue for inbound propagation.
Do the following:
1. Create the transformation function.
2. Grant EXECUTE to the MGW agent user or to PUBLIC on the function and the
object types it references.
3. Call dbms_transform.create_transformation to register the
transformation.
4. Call dbms_mgwadm.add_subscriber to create a MGW subscriber using the
transformation, or dbms_mgwadm.alter_subscriber to alter an existing
subscriber.
The value passed in the transformation parameter for these APIs must be the
registered transformation name and not the function name.
What happens if a transformation raises an exception?
If a transformation function raises an exception, a message conversion failure occurs
and will be indicated by an oracle.mgw.common.MessageException in the MGW
log file.
Frequently Asked Questions 6-13